The provision of sufficient bandwidth and reasonable efficiency of an antenna in a portable communication device is a general problem. Ideally, an antenna for radiation of electromagnetic waves at a given frequency should have dimensions larger than or equal to half the wavelength of the radiated waves at that frequency. At 860 MHz, e.g., the wavelength in vacuum is around 35 cm. At 2.4 GHz, the wavelength in vacuum is around 12 cm. Thus for a state of the art communication device having external dimensions less than 6 cm (e.g. headsets) and even less than 5 cm and often less than 2 cm or 1 cm (e.g. hearing instruments), it can in practice difficult to provide an antenna with appropriate technical specifications at 2.4 GHz (in view of the typical limited power supply of a portable (e.g. battery driven) communication device).
US 2006/0109182 A1 describes an antenna device for a portable device having an antenna loop of conducting material to be connected to radio circuitry in the portable device. The antenna loop is positioned opposite a ground plane of a PCB. The antenna device also comprises at least one battery, which is positioned in the extension of a first side of the PCB, and acts as an extension of the ground plane of the PCB.
US 2006/0109183 A1 describes a folded wideband loop antenna comprising sections extending in first and second separate parallel planes, wherein the loop antenna sections form a three-dimensional structure having a substantial two-dimensional extension in at least one of the first and second planes.